• Affects of Earthquakes on Astronomy

    The Earthquake and Astronomy
    The earthquake in Japan on March 11, 2011 created astronomical headlines too.  You may have seen things like "Earthquake shortens day" or "Earth's axis shifted by earthquake."  While these appear to be true, they are certainly meant to get your attention, and may be a bit misleading.


    One of the things that every student learns in high school physics is Newton's third law:  "For every action, there is an equal and opposite reaction."  This is true in the lab, but is also true everywhere in the universe.  So when there is a major earthquake, things move, and there has to be a reaction.  The Earth pushes back.  So is this a big deal?  Probably not.


    Earthquakes are a very big deal to those of us living on the Earth's surface.  This one earlt 2011 in Japan demonstrated how bad:  the quake itself, the tsunamis, and problems compounded by those two events.  But for the planet as a whole, our place in space, and our long-term future, it is not such a big deal.


    Because of this 8.9 magnitude earthquake, the day did get a wee bit shorter:  We lost 0.0000016 seconds.  That is a lot of zeros, and makes for a very short timing change.  The axis did change its tilt a little, but it too is quite small.  The North Pole moved about 4 inches.


    For comparison, consider two recent major earthquakes:

    • 2/27/2010 in Chile, magnitude 8.8:  lost 0.00000126 seconds and moved about 3 inches.
    • 12/26/2004 near Sumatra, magnitude 9.1:  lost 0.0000068 seconds and moved 2.76 inches.

    Also consider that these changes have happened and do happen every time there is an earthquake.  For us Earth creatures, it will continue to be a bumpy ride, but there are really no long-term consequences to the planet from the day getting shorter or the axis changing its tilt due to earthquakes.


    For more information on major earthquakes of the past:



    Aaron Clevenson

    Lead Astronomer